Effect of Water on Keck’s Catalytic Asymmetric Allylations of Aldehydes

The complex generated from BINOL, Ti(i-PrO) 4 , and unactivated or a large amount of activated 4 A MS in toluene is very effective in catalytic allylations of aldehydes using allyltributyltin. Allylations with 2.5 mol% of the catalyst provide homoallylic alcohols with greater than 95% ee. Very high syn-selective allylations of protected b-hydroxyaldehydes are achieved with 5 mol% of the BINOL/Ti(i-PrO) 4 complex.